We saw the movie last night, and I understand that it's closely based on this book... tempted to buy it, but the price tag is intimidating. I may change my mind yet.
The stars, then, are for the movie. I was expecting it to be a generic kind of French biopic, and it really isn't! It's visually inventive (you can absolutely see that it started life as a graphic novel), informative without drowning you in detail, and packs a serious erotic charge. The actors were all terrific. Some people didn't like Laetitia Casta as Bardot

but personally I thought it was inspired casting. She does the vacuous sex-kitten thing perfectly. So what if she happens to be a vacuous sex-kitten in real life as well? Having Doug Jones as "La Gueule" (Gainsbourg's fantasy alter ego)

was even more inspired.
And it's really funny, especially at the beginning. The kid who plays young Gainsbourg is a natural. I loved the scene with him and the model at the life drawing class, and the bit where he offers to introduce the stuffed-shirt Vichy police officer to the SS lieutenant. "He could advance your career" says the little Jewish boy, completely straight-faced. Half the audience laughed out loud.